Generally, a vehicle is provided with a cooling system having a form of a heat exchanger such as a radiator or an oil cooler as well as an air conditioning system for cooling the interior of the vehicle.
The radiator is a component for preventing a temperature of an engine from being raised to a predetermined temperature or more, and a high temperature coolant absorbing heat generated by combustion while being circulated in the engine is circulated by a water pump to radiate heat to the outside while passing through the radiator. Therefore, the radiator is a heat exchanger preventing overheat of the engine and allowing an optimal driving state to be maintained.
In addition, oil is filled in a component such as the engine or a transmission of the vehicle in order to perform a lubrication action and maintain air-tightness. However, when the oil becomes excessively hot, a viscosity of the oil is decreased, such that the oil may not appropriately perform the lubrication action and air-tightness maintaining performance. Particularly, lubrication is not appropriately conducted, such that there is a risk that the component such as the engine, or the like will be damaged. A means cooling the oil in order to prevent such a phenomenon is an oil cooler.
Since a large amount of heat is generated from the engine during a period in which the vehicle is driven, the coolant and the oil become hot, and are thus cooled by the radiator and the oil cooler, respectively. Meanwhile, since a viscosity of the oil is increased when a temperature of the oil is lowered, in the case in which an external air temperature is very low in the cold latitudes or in winter, the oil is in a state in which the viscosity is raised to a required viscosity or more at the time of initial starting of the vehicle. However, when the oil in this state is further cooled using the oil cooler, there is a risk that the component such as the engine, or the like will be damaged. Such a phenomenon is called a cold shock, and several methods such as a method in which the oil cooler is not operated at the time of the initial starting, a method of operating a warmer, which is an apparatus of heating the oil, and the like, are used in order to prevent the cold shock.
FIG. 1 is a schematic view illustrating an oil heat exchange system for a vehicle according to the related art.
As illustrated in FIG. 1, in the oil heat exchange system for a vehicle according to the related art, a first circulation line 1 forming a coolant flow in which a coolant heated by an engine 10 passes through a heater core 20 heating air for heating the interior of the vehicle and is then introduced again into the engine 10 to be circulated is formed. Here, the coolant passing through the heater core 20 may be controlled by a first control valve 25 to pass through a warmer 30 and be then introduced into the engine 10 or bypass the warmer 30 without passing through the warmer 30 and be directly introduced into the engine 10. In addition, a second circulation line 2 forming a coolant flow in which the coolant heated by the engine 10 passes through a radiator 50 cooling the coolant using external air and is then introduced again into the engine 10 to be circulated is formed, separately from the first circulation line 1. Here, an oil cooler 40 is mounted in the radiator 50. In addition, a third circulation line 3 is formed so that oil for a transmission is circulated therethrough, and the oil discharged from the transmission 11 is controlled by a second control valve 35 to pass through the warmer 30 or pass through the oil cooler 40 and be then introduced again into the transmission 11 depending on a temperature of the oil.
Here, when the oil is heated while a high temperature coolant passing through the warmer 30 at the time of initial starting of the vehicle, fuel efficiency of the vehicle is improved, but a heat source of the coolant is utilized to heat the oil, and a heat source of the heater core 20 heating the interior of the vehicle using the heat source of the coolant is thus insufficient, such that sufficient heating performance may not be obtained. Therefore, the first control valve (a bypass valve) 25 controlling a flow rate of the coolant introduced into the warmer 30 to heat the oil while securing heating performance of the interior at the time of the initial start of the vehicle is mounted in front of the warmer 30.
In more detail, a wax encapsulation type thermostat of which a volume is changed depending on a temperature is generally used as the first control valve 25. In this case, as a temperature of the coolant introduced into the warmer 30 rises, wax is expanded to open a valve. Therefore, a flow rate of the bypassed coolant is decreased, and a flow rate of the coolant introduced into the warmer 30 is increased to heat the oil.
However, in the oil heat exchange system for a vehicle according to the related art as described above, the first control valve should be mounted in order to control the flow rate of the coolant introduced into the warmer, and a structure of a coolant channel for this purpose becomes complicated, such that it is not easy to manufacture the coolant channel, and pressure loss of the coolant is generated by the first control valve and the complicated coolant channel.